This research proposal is concerned with the mental representation and processes that underlie spoken work recognition. The long-term objective of the proposed research is to more fully understand the human listener's remarkable ability to recognize spoken words so rapidly and efficiently. In particular, the proposed research is aimed at identifying the cognitive and perceptual mechanisms that enable the listener to isolate a given work from among tens of thousands of lexical representation in memory in a fraction of a second. The specific aims of this proposal focus on extending and elaborating two related models of spoken word recognition, the Neighborhood Activation Model and a derived connectionist instantiation of this model called PARSYN. Three empirical projects are proposed that focus on the nature of lexical representations in perceptual processing, constraints on lexical activation in memory, and possible mechanisms for parsing words from the speech stream. Each of these projects is directly motivated by the model PARSYN an focuses on the interface between phonetic processing and lexical discrimination in memory. In order to address these issues, a number of different experimental paradigms and stimuli will be employed. The experimental paradigms include accustic-phonetic and semantic priming tasks, auditory lexical decision tasks, naming tasks, and monitoring tasks. Specially constructed word and nonword stimuli will be generated to test the specific issues cited above. The proposed research is intended to provide deeper insights into the mental processes responsible for the uniquely human capacity for spoken language comprehension. This basic research should have important implications for understanding both normal and disordered communication systems that depend on the spoken word.